Chapter 467: Medical Evaluation of the Surgical Patient

Cardiovascular and pulmonary complications continue to account for major morbidity and mortality in patients undergoing noncardiac surgery. Emerging evidence-based practices dictate that the internist should perform an individualized evaluation of the surgical patient to provide an accurate preoperative risk assessment and stratification that will guide optimal perioperative risk-reduction strategies. This chapter reviews cardiovascular and pulmonary preoperative risk assessment, emphasizing the goal-directed management of patients at elevated risk for adverse cardiovascular outcomes in the perioperative period. In addition, perioperative management of diabetes mellitus and prophylaxis of endocarditis and for venous thromboembolism are reviewed.

Simple, standardized preoperative screening questionnaires, such as the one shown in Table 467-1, have been developed for the purpose of identifying patients at intermediate or high risk who may benefit from a more detailed clinical evaluation. Evaluation of such patients for surgery should always begin with a thorough history and physical examination and with a 12-lead resting electrocardiogram, in accordance with the American College of Cardiology/American Heart Association guidelines. The history should focus on symptoms of occult cardiac or pulmonary disease. The urgency of the surgery should be determined, as true emergency procedures are associated with unavoidably higher morbidity and mortality risk. Preoperative laboratory testing should be carried out only for specific clinical conditions, as noted during clinical examination. Thus, healthy patients of any age who are undergoing elective surgical procedures without coexisting medical conditions should not require any testing unless the degree of surgical stress may result in unusual changes from the baseline state.

A stepwise approach to cardiac risk assessment and stratification in patients undergoing noncardiac surgery is illustrated in Fig. 467-1. The evaluation begins with characterization of the combined surgical and clinical risk into categories of low (<1%) and elevated risk for major adverse cardiovascular events (MACE). Select surgeries are associated with very low risk for MACE; these surgeries and procedures include select ophthalmologic surgeries (e.g., cataract surgery), select endoscopic procedures, and select superficial procedures. Patients undergoing these low-risk procedures should proceed to surgery without further testing. Clinical risk may be estimated with the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) risk calculator (http://www.riskcalculator.facs.org) or with calculation of the Revised Cardiac Risk Index (RCRI).

Previous studies have compared several cardiac risk indices. The American College of Surgeons’ National Surgical Quality Improvement Program prospective database has identified five predictors of perioperative myocardial infarction (MI) and cardiac arrest based on increasing age, American Society of Anesthesiologists class, type of surgery, dependent functional status, and abnormal serum creatinine level. However, given its accuracy and simplicity, the RCRI (Table 467-2) is often the favored risk index. The RCRI relies on the presence or absence of six identifiable predictive factors: high-risk surgery, ischemic heart disease, congestive heart failure, cerebrovascular disease, diabetes mellitus treated with insulin, and renal insufficiency with a creatinine >2.0 mg/dL. Each of these predictors is assigned one point. The risk of major cardiac events—defined as MI, pulmonary edema, ventricular fibrillation or primary cardiac arrest, and complete heart block—can then be predicted. Based on the presence of none, one, two, three, or more of these clinical predictors, the rate of development of one of these four major cardiac events is estimated to be 0.4, 0.9, 7, and 11%, respectively (Fig. 467-2). An RCRI score of 0 signifies a 0.4–0.5% risk of cardiac events; RCRI 1, 0.9–1.3%; RCRI 2, 4–7%; and RCRI ≥3, 9–11%. The clinical utility of the RCRI is to identify patients with three or more predictors who are at very high risk (≥11%) for cardiac complications and who may benefit from further risk stratification with noninvasive cardiac testing, initiation of preoperative preventive medical management, or avoidance of surgery.

For patients at elevated combined clinical and surgical risk for MACE, the stepwise perioperative cardiac assessment for coronary artery disease (CAD) proceeds with consideration of functional capacity. Participation in activities of daily living offers an expression of functional capacity, often expressed in terms of metabolic equivalents (METs). For predicting perioperative events, poor exercise tolerance has been defined as the inability to walk four blocks or climb two flights of stairs at a normal pace or to meet a MET level of 4 (e.g., carrying objects of 15–20 lb or playing golf or doubles tennis) because of the development of dyspnea, angina, or excessive fatigue (Table 467-3). Patients with moderate or greater (≥4 METs) functional capacity (e.g., climbing up a flight of stairs, walking up a hill, or walking on level ground at 4 mph) generally should not undergo further non-invasive cardiac testing prior to elective non-cardiac surgery. Those patients with poor (<4 METs) or unknown functional capacity should undergo pharmacological stress testing if the results of such testing would impact decision-making or perioperative care.

PREOPERATIVE NONINVASIVE CARDIAC TESTING FOR RISK STRATIFICATION

There is little evidence to support widespread application of preoperative noninvasive cardiac testing for all patients undergoing major surgery. The current paradigm to guide the need for noninvasive cardiac testing is to perform such testing in patients with poor or unknown capacity if it would alter clinical management or modify perioperative care. Options for pharmacological stress testing include dobutamine stress echocardiography or myocardial perfusion imaging with coronary vasodilator stress (dipyridamole, adenosine, or regadenoson) with thallium-201 and/or technetium-99m. Routine screening with noninvasive stress testing is not recommended in patients at low risk for noncardiac surgery. Furthermore, coronary revascularization before noncardiac surgery is not recommended for the express purpose of reducing perioperative cardiac events. That said, revascularization before noncardiac surgery should be considered in patients if it would be indicated regardless of the surgery planned and instead according to clinical practice guidelines. In the Coronary Artery Revascular Prophylaxis trial, there were no differences in perioperative and long-term cardiac outcomes with or without preoperative coronary revascularization; of note, patients with left main disease were excluded.

RISK MODIFICATION: PREVENTIVE STRATEGIES TO REDUCE CARDIAC RISK

Perioperative Coronary Revascularization

Prophylactic coronary revascularization with either coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) provides no short- or mid-term survival benefit for patients without left main CAD or three-vessel CAD in the presence of poor left ventricular systolic function and is not recommended for patients with stable CAD before noncardiac surgery. Although PCI is associated with lower procedural risk than is CABG in the perioperative setting, the placement of a coronary artery stent soon before noncardiac surgery may increase the risk of bleeding during surgery if dual antiplatelet therapy (DAPT) (aspirin and thienopyridine) is administered; moreover, stent placement shortly before noncardiac surgery increases the perioperative risk of MI and cardiac death due to stent thrombosis if such therapy is withdrawn prematurely (Chap. 270). It is recommended that, if possible, elective noncardiac surgery be delayed 30 days after placement of a bare metal intracoronary stent and ideally for 6 months after deployment of a drug-eluting stent. Contemporary stent platforms allow for greater flexibility in the earlier interruption of DAPT; current clinical practice guidelines do suggest consideration of elective noncardiac surgery 6 months after drug eluting stent (DES) implantation if the risk of further delaying surgery exceeds the risk of stent thrombosis/myocardial ischemia. For patients who must undergo noncardiac surgery early (>14 days) after PCI, balloon angioplasty without stent placement appears to be a reasonable alternative because DAPT is not necessary in such patients.

PERIOPERATIVE PREVENTIVE MEDICAL THERAPIES

The goal of perioperative preventive medical therapies with β-adrenergic antagonists, hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins), and antiplatelet agents is to reduce perioperative adrenergic stimulation, ischemia, and inflammation, all of which are heightened during the perioperative period.

B-ADRENERGIC ANTAGONISTS

The use of perioperative beta blockade should be based on a thorough assessment of a patient’s perioperative clinical and surgery-specific cardiac risk (e.g., as with the RCRI). The paradigm for beta blockade in the perioperative period has shifted in recent years owing, firstly, to the publication of the PeriOperative Ischemic Evaluation (POISE) trial demonstrating that, while perioperative beta blockade reduces the perioperative risk for MI, this is at the expense of increased death and stroke. Regarding POISE, this trial has been criticized for the use of an excessive dose of beta blocker in the perioperative period and one that may not be reflective of clinical practice, nor one that was titrated in the days or weeks preceding the procedure or surgery. Secondly, research misconduct has discredited the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echocardiography (DECREASE) family of studies, which previously contributed to the bedrock of data supporting the use of perioperative beta blockade but have now been retracted.

Current guidelines emphasize the following key points:

1. Continuation of beta blockade in patients undergoing surgery and who have been receiving such therapy chronically.

2. Avoidance of beta-blocker withdrawal or initiation on the day of surgery.

3. Consideration of initiation of beta-blocker therapy perioperatively (ideally far enough in advance to assess safety and tolerability) in very select high-risk patients, namely, those with intermediate- or high-risk ischemia or three more RCRI risk factors.

HMG-COA REDUCTASE INHIBITORS (STATINS)

A number of prospective and retrospective studies support the perioperative prophylactic use of statins for reduction of cardiac complications in patients with established atherosclerosis. For patients undergoing noncardiac surgery and currently taking statins, statin therapy should be continued to reduce perioperative cardiac risk. Initiation of statin therapy is reasonable for patients undergoing vascular surgery independent of clinical risk. Perioperative initiation of statin therapy should be considered in patients undergoing elevated risk procedures if there is an indication for such therapy separate from the surgery and according to clinical practice guidelines.

ANGIOTENSIN-CONVERTING ENZYME (ACE) INHIBITORS

It is important to maintain continuity of therapy with ACE inhibitors (when such therapy is used for the treatment of heart failure or hypertension).

ORAL ANTIPLATELET AGENTS

The 4- to 6-week period following implantation of an intracoronary stent (bare metal or drug eluting) constitutes the period of time of greatest risk for the development of stent thrombosis. If possible, noncardiac surgery should be avoided in this vulnerable period. The duration of DAPT thereafter is dictated by the circumstances in which PCI was performed and whether the indication was stable ischemic heart disease or acute coronary syndrome. For the former among patients treated with a drug eluting stent, dual anti-platelet therapy should be given for at least 6 months. For the latter, dual anti-platelet therapy should be given for at least 12 months. However, DAPT may be interrupted to allow for noncardiac surgery 30 days after BMS and 6 months after DES, respectively. If P2Y₁₂ inhibitor therapy (clopidogrel, prasugrel, or ticagrelor) is interrupted or discontinued in patients who have received intracoronary stents, aspirin should be continued perioperatively (save select circumstances where the risk of bleeding may be catastrophic as in neurosurgical or spinal procedures) and the P2Y₁₂ receptor inhibitor should be restarted as soon as possible post-operatively. Decisions surrounding antiplatelet management in the perioperative setting among patients who have received intracoronary stents are complex and should involve multidisciplinary decision-making.

ALPHA₂ AGONISTS

Based on the results of POISE-2 (a large multicenter, international, blinded randomized clinical trial of aspirin and clonidine), α₂ agonists for prevention of cardiac events are not recommended in patients who are undergoing noncardiac surgery. In this trial, clonidine increased the rate of nonfatal cardiac arrest and clinically important hypotension, while reducing the rate of death or nonfatal MI.

CALCIUM CHANNEL BLOCKERS

Evidence is lacking to support the use of calcium channel blockers as a prophylactic strategy to decrease perioperative risk in major noncardiac surgery.

ANESTHETICS

Mortality risk is low with safe delivery of modern anesthesia, especially among low-risk patients undergoing low-risk surgery (Table 467-4). Inhaled anesthetics have predictable circulatory and respiratory effects: all decrease arterial pressure in a dose-dependent manner by reducing sympathetic tone and causing systemic vasodilation, myocardial depression, and decreased cardiac output. Inhaled anesthetics also cause respiratory depression, with diminished responses to both hypercapnia and hypoxemia, in a dose-dependent manner; in addition, these agents have a variable effect on heart rate. Prolonged residual neuromuscular blockade also increases the risk of postoperative pulmonary complications due to reduction in functional residual lung capacity, loss of diaphragmatic and intercostal muscle function, atelectasis, and arterial hypoxemia from ventilation-perfusion mismatch.

Several meta-analyses have shown that rates of pneumonia and respiratory failure are lower among patients receiving neuroaxial anesthesia (epidural or spinal) rather than general anesthesia. However, there were no significant differences in cardiac events between the two approaches. Evidence from a meta-analysis of randomized controlled trials supports postoperative epidural analgesia for >24 h for the purpose of pain relief. However, the risk of epidural hematoma in the setting of systemic anticoagulation for venous thromboembolism prophylaxis (see below) and postoperative epidural catheterization must be considered.

Perioperative pulmonary complications occur frequently and lead to significant morbidity and mortality. Clinical practice guidelines recommend the following:

1. All patients undergoing noncardiac surgery should be assessed for risk of pulmonary complications (Table 467-5).

2. Patients undergoing emergency or prolonged (3–4 h) surgery; aortic aneurysm repair; vascular surgery; major abdominal, thoracic, neurologic, head, or neck surgery; and general anesthesia should be considered to be at elevated risk for postoperative pulmonary complications.

3. Patients at higher risk of pulmonary complications should undergo incentive spirometry, deep-breathing exercises, cough encouragement, postural drainage, percussion and vibration, suctioning and ambulation, intermittent positive-pressure breathing, continuous positive airway pressure, and selective use of a nasogastric tube for postoperative nausea, vomiting, or symptomatic abdominal distention to reduce postoperative risk. Multiple pulmonary risk indices are available to estimate the postoperative risk of respiratory failure, pneumonia, and other pulmonary complications; among these is the ARISCAT risk index, which accounts for the following seven risk factors: age, low preoperative oxygen saturation, respiratory infection within the preceding month, upper abdominal or thoracic surgery, surgery lasting >2 h, and emergency surgery (Table 467-6).

4. Preoperative spirometry and chest radiography should not be used routinely for predicting risk of postoperative pulmonary complications but may be appropriate for patients with chronic obstructive pulmonary disease or asthma.

5. Spirometry is of value before lung resection in determining candidacy for coronary artery bypass; however, it does not provide a spirometric threshold for extrathoracic surgery below which the risks of surgery are unacceptable.

6. Pulmonary artery catheterization, administration of total parenteral nutrition (as opposed to no supplementation), or total enteral nutrition have no consistent benefit in reducing postoperative pulmonary complications.

DIABETES MELLITUS

(See also Chaps. 396–398) Many patients with diabetes mellitus have significant symptomatic or asymptomatic CAD and may have silent myocardial ischemia due to autonomic dysfunction. Intensive (versus lenient) glycemic control in the perioperative period is generally not associated with improved outcomes, and may increase the risk of hypoglycemia. Practice guidelines advocate a target glucose range from 100 to 180 mg/dL in the perioperative period. Oral hypoglycemic agonists should not be given on the morning of surgery. Perioperative hyperglycemia should be treated with IV infusion of short-acting insulin or SC sliding-scale insulin. Patients whose diabetes is diet controlled may proceed to surgery with close postoperative monitoring.

INFECTIVE ENDOCARDITIS

(See also Chap. 123) Prophylactic antibiotics should be administered to the following patients before dental procedures that involve manipulation of gingival tissue, manipulation of the periapical region of teeth, or perforation of the oral mucosa: those with prosthetic cardiac valves (including transcatheter prosthetic valves); prosthetic material used in valve repair (annuloplasty ring or artificial chord); previous infective endocarditis; cardiac transplant recipients with valvular regurgitation from a structurally abnormal valve; and unrepaired cyanotic congenital heart disease or repaired congenital heart disease, with residual shunts or valvular regurgitation at the site of adjacent to the site of a prosthetic patch or prosthetic device.

VENOUS THROMBOEMBOLISM

(See also Chap. 273) Perioperative prophylaxis of venous thromboembolism should follow established guidelines of the American College of Chest Physicians. Aspirin is not supported as a single agent for thromboprophylaxis. Low-dose unfractionated heparin (≤5000 units SC bid), low-molecular weight heparin (e.g., enoxaparin, 30 mg bid or 40 mg qd), or a pentasaccharide (fondaparinux, 2.5 mg qd) is appropriate for patients at moderate risk; unfractionated heparin (5000 units SC tid) is appropriate for patients at high risk. Graduated compression stockings and pneumatic compression devices are useful supplements to anticoagulant therapy or in patients at excessive bleeding risk.